Welcome to scuba diving, which, for all of us and every day, involves intelligent assessment of risk. As Walter is wont to say, the only way to be perfectly safe when diving is not to do it
So, let's look at the risks involved in diving alone in your lake, in 8' of water.
1. Entanglement. This is the big one. Getting entangled and not being able to fix it is a lethal problem. It's easy to understand being scared of entanglement in monofilament, because it's hard to see, but you can be lethally entangled in much heavier material. (We had a rebreather diver die here a while back from what appears to have been getting entangled in a buoy chain, in pretty shallow water.) Simple entanglements with a bit of monofilament may be easy to solve with a cutting device. More extensive ones may require getting out of your gear, which is something you practiced in your OW class, but have probably not practiced since, and it's a lot to ask of a new diver in a stressful circumstance. Of course, in 8' of water, you can get out of your gear and go to the surface (remembering to exhale, of course!) If the water in which you are diving is quite clear, and your surface support can see you have a problem, they may be able to freedive down to assist you. If the water is murky, the first they'll know of a problem is when your bubbles stop, which is a bit late . . .
2. Visibility. Many lakes, because of the lack of water movement in them, have very silty bottoms. Just wading into the lake will make the water turbid, and poor finning technique (as most of us had at the beginning) will continue to churn up the bottom (especially in such shallow water) and you could find yourself in a zero visibility situation very easily. Now, zero viz in 8 feet of water isn't a problem, as long as you remain calm, but it is a situation where some people get vertigo, and you have to retain the presence of mind to watch your gauge and head for the surface. Practicing useful scuba skills in such conditions will be difficult at best.
3. Equipment issues. You aren't very familiar with your equipment yet, and probably don't have much experience in managing anything that doesn't work. It's highly unlikely that something will happen that will kill you in 8 feet of water, but panicking because something HAS happened, and bolting to the surface, can.
So I would say that, if your water is clear and you can maintain surface support, and the area is free of significant entanglement hazards, the risk of practicing in your lake is low enough that I would accept it for myself. You have to think it through for yourself, and you may decide something different.
I have done a lot of solo practice in my own swimming pool, and not all of it has been with anyone else home. But the big thing is that I know my own temperament, and I feel very confident that nothing that can happen in my pool will cause me to lose my cool. I have some basis for that, because I've been through a lot of deliberately stress-inducing training. A new diver really doesn't know that about himself, which is why there is still some risk, even in that benign environment.